The nurses always have trouble getting the IV started on me too. I've had so much IV steroids over the past 5 years that my veins are shot. Usually they have to get a IV therapist to start the IV and they put in a heplock port for the 2 or 3 days. That might be what the nurse was talking about, that way they don't have to start a new line each day.
Last time I had an MRI, the tech had trouble starting the IV for the GAD! It took 3 sticks! So I know exactly how you feel! I am in a clinical trial so I have an MRI every month with GAD. Not fun...and then they have to draw tons of blood from me (Taffy don't look!

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One thing I might suggest is making sure you drink plenty of fluids the day before you have the IV done and warm up your arm. That seems to help. Warm veins pop out a little better and the vampires don't have to go deep sea (see) diving looking for them! LOL!